The present invention relates to coated medical devices, and more particularly to medical devices that are coated using air suspension.
It is often beneficial to coat medical devices so that the surfaces of such devices have desired properties or effects. For example, it is useful to coat medical devices to provide for the localized delivery of therapeutic agents to target locations within the body, such as to treat localized disease (e.g., heart disease) or occluded body lumens. Such localized drug delivery avoids the problems of systemic drug administration, which may be accompanied by unwanted effects on parts of the body which are not to be treated, or because treatment of the afflicted part of the body requires a high concentration of therapeutic agent that may not be achievable by systemic administration. Localized drug delivery is achieved, for example, by coating balloon catheters, stents and the like with the therapeutic agent to be locally delivered. The coating on medical devices may provide for controlled release, which includes long-term or sustained release, of a bioactive material.
Aside from facilitating localized drug delivery, medical devices are coated with materials to provide beneficial surface properties. For example, medical devices are often coated with radiopaque materials to allow for fluoroscopic visualization during placement in the body. It is also useful to coat certain devices to achieve enhanced biocompatibility and to improve surface properties such as lubriciousness.
Conventionally, coatings have been applied to medical devices by processes such as dipping, spraying, vapor deposition, plasma polymerization, and electrodeposition. Although these processes have been used to produce satisfactory coatings, there are numerous potential drawbacks associated therewith. For example, it is often difficult to achieve coatings of uniform thicknesses, both on individual parts and on batches of parts. Also, many of these conventional coating processes require that the coated part be held during coating, resulting in defects such as bare spots where the part was held and thus requiring subsequent coating steps. Further, many conventional processes require multiple coating steps or stages for the application of a second coating material, or to allow for drying between coating steps or after the final coating step.
There is, therefore, a need for a cost-effective method of coating medical devices that results in uniform, defect-free coatings and uniform drug doses per unit device. The method would allow for a multiple stage coating in order to apply a bioactive material that may be environmentally sensitive, e.g., due to heat and light (including ultra-violet) exposure and due to degradation of the bioactive material due to process-related forces (e.g., shear). The method would thus allow for better control of the sensitivity of the bioactive material and reduce any potential degradation due to environmental issues. The method would also reduce variations in the coating properties.
In one aspect, the present invention relates to methods for coating at least a portion of a medical device which is used, at least in part, to penetrate the body of a patient. In one embodiment, the method comprises the steps of suspending the medical device in an air stream that is substantially devoid of suspending particles and introducing a coating material into the air stream such that the coating material is dispersed therein and coats at least a portion of the medical device. This process is used to apply one or more coating materials, simultaneously or in sequence. In certain embodiments of the invention, the coating materials include therapeutic agents, polymeric materials, and sugars, waxes, and fats. A coating substance that is comprised of suspension particles may be utilized that are fused to the surface of the medical device by a coating solution.
In another embodiment of the present invention, the medical devices are suspended in an air stream substantially devoid of suspending particles and a coating apparatus coats at least a portion of the medical device with a coating material while the medical devices are suspended in the air stream. The coating apparatus may include a device that utilizes any number of alternative coating techniques for coating the medical devices.
In another aspect, the present invention relates to coated medical devices made by the method of the invention.
One advantage of the present invention is that it provides coated medical devices with uniform coating thicknesses and mechanical properties and minimal contaminants.
Another advantage of the present invention is that it allows simultaneous coating of multiple numbers of medical devices at the same time, thus leading to higher process efficiency.
Another advantage of the present invention is that it does not require that the medical device be held during the coating process, thereby eliminating bare spots and the need for subsequent coating steps to coat such bare spots.
Another advantage of the present invention is that it provides a method for coating medical devices by coating materials that are otherwise difficult to use, such as incompatible, insoluble/suspension, or unstable coating solutions.
Another advantage of the present invention is that it reduces human exposure to materials used in conventional coating processes such as solvents, polymers, drugs, and the like.
Another advantage of the present invention is that it allows for the application of multiple coating materials to numerous medical devices in a single batch coating process.
Yet another advantage of the present invention is that it provides a method for coating a medical device that results in a uniform drug dose per unit device.